The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Internal combustion engines combust an air and fuel mixture within cylinders to drive pistons, which produces drive torque. Airflow into the engine is regulated via a throttle. More specifically, the throttle adjusts throttle area, which increases or decreases airflow into the engine. As the throttle area increases, the airflow into the engine increases. A fuel control system adjusts the rate that fuel is injected to provide a desired air/fuel mixture to the cylinders and/or to achieve a desired torque output. Increasing the amount of air and fuel provided to the cylinders increases the torque output of the engine.
In spark-ignition engines, spark initiates combustion of an air/fuel mixture provided to the cylinders. In compression-ignition engines, compression in the cylinders combusts the air/fuel mixture provided to the cylinders. Spark timing and air flow may be the primary mechanisms for adjusting the torque output of spark-ignition engines, while fuel flow may be the primary mechanism for adjusting the torque output of compression-ignition engines.
Boosted engines include a boost device, such as a turbocharger or a supercharger, which provides pressurized air to an intake manifold of an engine. The pressurized air increases the compression ratio of the engine, which increases the torque output of the engine for a given amount of air and fuel provided to the cylinders. In this regard, a boost device may be used to increase the torque output of an engine and/or to improve the fuel economy of an engine.
Pre-ignition occurs in spark-ignition engines when an air/fuel mixture in a cylinder is ignited by an ignition source other than spark. Pre-ignition may cause noise and engine damage, and may even lead to engine failure. Regular pre-ignition occurs in one or more cylinders on a periodic basis (e.g., once per engine cycle). Stochastic pre-ignition occurs at random. Regular pre-ignition may repeatedly occur under certain engine operating conditions, while stochastic pre-ignition may be less repeatable.